Ultraviolet area sterilizer and method of area sterilization using ultraviolet radiation

ABSTRACT

An ultraviolet area sterilizer (UVAS) is mobile or stationary. The UVAS is positioned in a room, such an operating room or intensive care unit. Motion detectors sense movement, to assure that personnel have evacuated the space to be sterilized. Subsequently, UV-C generators, such as a bank of mercury bulbs, generate intense levels of UV-C. An array of multiple UV-C sensors scan the room, and determine the darkest area, or the area reflecting the lowest level of UV-C back to the sensors. A BASIC Stamp contained in the device calculates the time required to obtain a bactericidal dose of UV-C reflected back from darkest area. Once a bactericidal dose has been reflected to all the sensors, the unit notifies the operator and shuts down. By relying on reflected doses rather than direct exposure, the UVAS is able to sterilize or sanitize all surfaces within the room that are within view of an exposed wall or ceiling.

This invention claims priority of provisional application serial No.60/183,662, filed Feb. 18, 2000; and provisional application serial No.60/190,601, filed Mar. 20, 2000; and provisional application serial No.60/228,823, filed Aug. 28, 2000.

FIELD THE INVENTION

This invention relates to methods and devices for bacterial, fungaland/or viral sterilization, and is more particularly directed to amethod and device for sterilizing rooms and similar enclosed areas.

BACKGROUND OF THE INVENTION

Nosocomial, or hospital acquired, infections are common, costly, andsometimes lethal. A recent review of such infections in the cardiacsurgery unit of a major hospital revealed a nosocomial infection rate of27.3% that more than doubled the mortality rate for afflicted patients.The nature of bacteria acquired in the hospital setting differssignificantly from bacteria found in a community setting primarily intheir resistance to antibiotic therapy.

“Historically, staphylococci, pseudomonads, and Escherichia coli havebeen the nosocomial infection troika; nosocomial pneumonia, surgicalwound infections, and vascular access-related bacteremia have caused themost illness and death in hospitalized patients; and intensive careunits have been the epicenters of antibiotic resistance. Acquiredantimicrobial resistance is the major problem, and vancomycin-resistantStaphylococcus aureus is the pathogen of greatest concern. The shift tooutpatient care is leaving the most vulnerable patients in hospitals.Aging of our population and increasingly aggressive medical and surgicalinterventions, including implanted foreign bodies, organtransplantations, and xenotransplantation, create a cohort ofparticularly susceptible persons. Renovation of aging hospitalsincreases risk of airborne fungal and other infections.¹”

¹ Nosocomial infection update. Weinstein R. A. Cook County Hospital,Division of Infectious Diseases, Chicago, Ill. 60612 Emerg. Infect. Dis.1998 July-September;4(3):416-20

Significant morbidity, mortality, and costs are associated with theseinfections. Many factors contribute to these dangerous infections. Mostnotably are the overuse of antibiotics and poor personal hygiene such ashand washing. Abundant evidence exists, however, that the hospitalenvironment itself contributes to the problem by harboring virulentstrains of bacteria, fungi, and viruses, and that many methods commonlyused are ineffective and may actually spread contaminants.

Attempts to eradicate surface contaminates from the hospital settinghave varied greatly in strategy and success. These have ranged fromantiseptic soaps to fumigation with formaldehyde gas. Topicalantiseptics are problematic for several reasons. First, they haverecently been shown to actually induce antibiotic resistances and thusmay be adding to the problem. Secondly, many surfaces such as keyboards,television sets, and monitoring controls are difficult if not impossibleto decontaminate with liquid disinfectants without harming theelectronics. Gas disinfection, while effective, is time consuming,hazardous to workers, and environmentally unwise.

Ultraviolet (UV) light has been long used for disinfection andsterilization. Ultraviolet light may be produced artificially byelectric-arc lamps. Recently, the widespread availability of low tomedium pressure mercury bulbs has led to the development of deviceswhich use UV-C to decontaminate water supplies. UV-C is a high frequencywavelength of light within the ultraviolet band and has been shown to bethe most bactericidal type of ultraviolet light. UV-C has wavelengths ofabout 2800 Å to 150 Å. To date, there are no published efforts to useUV-C to decontaminate or disinfect larger areas such as operating rooms.The only recent availability of the appropriate bulbs as well assignificant safety concerns regarding worker exposure to UV-C likelycontribute to the lack of efforts to use UV-C outside of self-containedwater purification systems.

SUMMARY OF THE INVENTION

The ultraviolet area sterilizer of the present invention (UVAS) is anautomated room sterilizer. The unit may be mobile or stationary, withthe unit incorporated into the room design. The UVAS is positioned in aroom, such an operating room or intensive care unit, where concernexists regarding the presence of pathogenic bacteria on environmentalsurfaces. A wireless remote control may be used to activate the device.For an initial interval after actuation, motion detectors sensemovement, to assure that personnel have evacuated the space to besterilized. Subsequently, UV-C generators, such as a bank of mercurybulbs, generate intense levels of UV-C.

After the bulbs have reached a steady state of output, an array of UV-Csensors scan the room, and determine the darkest area, or the areareflecting the lowest level of UV-C back to the sensors. A BASIC Stampcontained in the device calculates the time required to obtain abactericidal dose of UV-C reflected back from darkest area. The UVAStransmits the calculated dose of UV-C, as well as other monitoringinformation, to the remote control where it is displayed to theoperator. Once a bactericidal dose has been reflected to all thesensors, the unit notifies the operator and shuts down. By relying onreflected doses rather than direct exposure, the UVAS is able tosterilize or sanitize all surfaces within the room that are within viewof an exposed wall or ceiling. The pathogenic bacteria in the room havebeen effectively eliminated.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of the device.

FIG. 2 is a side elevation of the device.

FIG. 3 is a front elevation of the device.

FIG. 4 is a schematic of the device.

FIG. 5 is a schematic of the controls of the device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawing figures, the UVAS is mounted on a rollingbase 2 to provide portability. FIG. 2. An adjustable handle 3 isprovided for transporting the device. The base includes a box 4 whichcould measure 30×20 cm, and in which is housed circuits, a power supplyfor the DC components, and the bulb ballasts. A central post rises 6from the base to an overall height of, for example, 220 cm.

Around the central post are banks of UV-C emitting bulbs. In theembodiment as shown, six pairs of medium pressure mercury bulbs 8 arepresent, with each pair positioned equidistant from the pair on eachside, so that they are present at 60° around the device. The bulbs maybe 48-inch long, 115-Watt germicidal lamps that produce 300 microwattsof ultraviolet radiation at 1 meter. Each pair of bulbs is preferred toprovide not less than 800 of coverage, so that 3600 coverage is assured.

A control box 10 on top of the unit contains wireless components, theUV-C sensor array, a bank of BASIC Stamps, motion detectors 12, andaudible 20 and visible alarms 22. A power switch 14 is provided on theexterior of the device. A series of plugs 16 for control functions arealso provided. A power cord 18 is provided.

Referring now to FIG. 4, three door contacts 24 are shown. Thesecontacts are placed in one or more of the doors of the room in which thedevice is operating. The door contacts are switches which disable thedevice if any one of the switches is opened, such as by opening thedoor. The connectors may be disabled in situations where they would beunnecessarily redundant. The motion detectors 12 are immediatelyactivated upon activation of the device and prior to powering of theballasts 26 and the bulbs, by means of the time delay 28. If the motiondetectors sense motion at any time during the operation of the device,power to the ballasts and the bulbs is immediately disabled. A preferredembodiment has three 120° passive ultrasonic motion detectors located ontop of the device to provide coverage about the entire perimeter of thedevice.

The UVAS is controlled by a series of programmable BASIC Stamps 32. TheBASIC Stamps are contained in the control box 10. BASIC Stamp® II, whichis available from Parallax, Inc of Rocklin, Calif. may be used.

The BASIC Stamps continuously receive a voltage input from sensors whichreceive reflected UV-C radiation. The sensors continuously sense thelevel of UV-C radiation which is reflected back to the device from 360°around the device. Eight sensors may be used. Each sensor converts themeasurement of the level of radiation to a voltage output, which istransmitted to the BASIC Stamp. The BASIC Stamp samples the voltagereceived at intervals and adds the cumulative total of the voltagereceived. When the BASIC Stamp determines that the reflected UV-Cradiation received by each and every sensor has reached thepredetermined minimum cumulative total, the BASIC Stamp causes thedevice to shut down, and a signal is given to the operator that theprocess has been completed. The BASIC Stamp is programmable to measurevoltage inputs as required by the particular application.

The BASIC Stamps receive commands from a wireless remote control 30. Aswitch activates the remote control. Entry of a security code allows theoperator to begin sending commands to the bank of BASIC Stamps. Commandsinclude Activate, Shutdown, enter Sterilization Mode, or enter SanitizeMode. The remote is in two-way communication with the UVAS and displaysdata from the sensor array, time left to sterilize or sanitize the room,and in case of bulb failure, the status of all numbered bank of bulbs.If two-way communication with the remote is lost, the unit shuts down.

The BASIC Stamps activate the motion detectors at least one minute priorto activation of the UV-C bulbs and continue to monitor the detectors.They perform all calculations regarding bactericidal doses, storecumulative dosing data, and system checks to alert the operator of bulbfailure. This is needed since no one can actually look at the unit tocheck for burned out bulbs or damaged banks. The stamps can beprogrammed by attaching them to a personal computer via a serial portconnection, thus allowing alteration to the algorithms to accommodatespecial circumstances.

An example of a protocol for using the device is described.

1. An operator rolls the UVAS into the room to be sterilized. Afterchecking the room for occupants, the operator leaves with the remotecontrol.

2. After securing the room, the operator enters into the remote controla security code, whereupon the operator is prompted to press an “on”switch on the remote control, activating the UVAS.

3. The audible voice alarms and the motion detectors activate and stayon until the entire cycle has been complete. Should the UVAS detectmotion, the unit automatically deactivates itself until the operatorre-enters the room and trips a breaker, thus preventing the operatorfrom re-activating the unit and harming an occupant present in the room.

4. The motion detectors stay on for a preset time, such as one minute,prior to powering the mercury bulbs and then stay active until the cycleis complete and the bulbs are powered down.

5. The bulbs are powered, and when sufficient time has elapsed to allowthe bulbs to reach a steady state output (one minute or less), the BASICStamp reads data from all the individual sensors located on the array.The array senses 360 degrees at a minimum with overlapping of theirwindow of view. They are oriented away from the UVAS, thus measuring thedose of UV-C reflected back to the unit. This data is fed into themicrocontroller where it is integrated to compute cumulative exposure ofUV-C reflected back from each sensor in the array.

6. Based on the least reflective surface or direction (of severalthousand “snapshots”) the microcontroller calculates the time the unitwill need to stay activated to allow a bactericidal dose of UV-C to bereflected back to the unit from all directions.

7. Once sufficient time for a lethal dose of UV-C to be reflected backto the unit has elapsed, the unit powers down the bulbs and sounds an“All Clear” alert to the operator.

Upon completion of the cycle, the unit has sterilized all the exposedsurfaces within the room, including the primary shadows such as the backor wall side of all rails, cabinets which are not against the wall, andtables. Surfaces not directly exposed to the UV-C are sterilized by UV-Creflected from the walls and ceilings.

Trials of the UVAS in actual operating rooms and endoscopy suites andexam rooms as well as simulated trials have been performed. At directexposure from two meters, the unit is able to reduce colony counts ofcommon hospital pathogens (staphaloccocus Aureus, pseudomonas, andEscherichia coli) by a minimum of 99.9% in one minute and achievedsterilization in 10 minutes. Five of nine surfaces were completelysterile after one minute. Subsequent trials of a unit modified toincrease reflectance off the unit itself sterilized the surfaces of thesame bacterial species within one minute. In one trial, the back of anexam chair was contaminated with pseudomonas, Escherichia coli, andstaphylococcus aureaus bacteria from slurries prepared by a hospitalmicrobiology lab. The surface was the cultured for a control prior tousing the unit and were shown to grow greater than 100,000 colonies ofbacteria. It was then cultured at ten minutes and twenty minutes afteractivation of the unit. The test surface was not in direct line of sightof the UVAS and received only reflected doses of UV-C. Cultures usingconvex agar plates designed for surface cultures were used and incubatedby a hospital microbiology lab. The control cultures grew greater than100,000 colonies of all three species. The ten minute and twenty minutecultures showed no growth, demonstrating the ability of the unit tosterilize surfaces using only reflected doses.

The estimated reflection from the wall in the test room was only 3%.Reflection below three percent is not desirable, since the increasedexposure time required to achieve an effective dose may result indegradation of articles which are present in the room and which areexposed to direct UV-C radiation. Through the use of paint that producesa painted wall which reflects 50-85% of the UV-C, the efficiency of thedevice is increased, allowing for greatly decreased exposure times.

In most environments, there is a presence of what microbiology labslabel as “wild spore forms” of bacteria. These bacteria are not known tocause human disease, and yet, are resistant to low doses of UV-C. Thedual programming modes of the unit allow treatment as required. One mode(Sanitize) kills all known pathogens and requires a lower exposure andthus shorter time. The other mode (Sterilize) kills all species ofbacteria and requires greater cumulative doses and therefore more time.

The Ultraviolet Area Sterilizer self monitors bactericidal levels.Reflected doses of UV-C are measured, and the device remains activateduntil bactericidal levels are received. This ensures that areas inrelative shadow and not in direct line of sight with the unit aresterilized. Also, the unit can be set to sanitize (kill commonpathogens) or sterilize (kill all microbes).

Without adequate safety features, daily use of intense UV-C is dangerousand impractical. The device has motion detectors which assure the roomis vacant of personnel prior to activation. Hard wired plugs on the unitare available for additional door, window, or other entry monitoringdevices special situation may dictate. Once activated, the unit shutsdown instantly when motion occurs anywhere in the room being sterilized.If the UVAS loses two-way communication with the remote control it alsoshuts down. In daily use, safety protocols commonly used in hospitalssuch as those in use for laser and x-ray devices may be implemented.

The UVAS is able to sanitize or sterilize all exposed surfaces in aroom. It is able to do so safely, leave no residual toxins or radiation,and generates no adverse environmental side products. In addition, theUVAS is able to notify the operator of the time required to perform thistask and automatically shuts down upon completion of sterilization. Theinventor has performed tests to prove the efficacy of the UVAS, all ofwhich have been successful. The only limiting factor encountered to dateis the reflectivity of some paints and other surfaces which absorbrather than reflect UV-C, requiring prolonged exposures of twentyminutes or greater. Specially reflective paints may be included in thismethod of area sterilization.

What is claimed is:
 1. A method of sterilizing an area using ultravioletradiation, comprising the steps of: (a) causing ultraviolet-C radiationto be emitted within an enclosed area; (b) measuring a reflection ofultraviolet-C radiation from each of multiple points within saidenclosed area; (c) calculating the ultraviolet-C radiation levelnecessary to sterilize said enclosed area and comparing it with themeasured reflected ultraviolet-C radiation; (d) terminating the emissionof ultraviolet-C radiation after determining that the required minimumultraviolet-C radiation has been reflected from each of said multiplepoints within said enclosed area.
 2. A method of sterilizing an areausing ultraviolet radiation as described in claim 1, wherein motionwithin said enclosed area is detected prior to the initiation ofemission of ultraviolet-C radiation.
 3. A device for sterilizing an areausing ultraviolet radiation, comprising: (a) a base; (b) a plurality ofultraviolet-C radiation emitters, wherein said plurality ofultraviolet-C radiation emitters are positioned on said base to emitultraviolet-C radiation 360 degrees around said base and above saidbase; (c) at least one radiation sensor which is attached to said basewhich receives reflected ultraviolet-C radiation from multiple points inan area that is external to the device, wherein said sensor measuressaid reflected ultraviolet-C radiation.
 4. A device for sterilizing anarea using ultraviolet radiation as described in claim 3, furthercomprising a motion detector which communicates with said plurality ofultraviolet-C radiation emitters.
 5. A device for sterilizing an areausing ultraviolet radiation as described in claim 3, wherein said areathat is external to the device is a room.
 6. A method of disinfecting anarea using ultraviolet radiation, comprising the steps of: (a) causingan emission of ultraviolet-C radiation within an enclosed area; (b)providing at least one sensor that receives only reflected ultraviolet-Cradiation from said emission of ultraviolet-C radiation; (c) measuring alevel of reflected ultraviolet-C radiation received by said at least onesensor; and (d) terminating the emission of ultraviolet-C radiation upondetermining that a cumulative level of reflected ultraviolet-C radiationhas been received by said at least one sensor.
 7. A method ofdisinfecting an area using ultraviolet radiation as described in claim6, wherein said enclosed area is a room having a plurality of walls, andwherein a portion of said emission of ultraviolet-C radiation isreflected from said plurality of walls, and wherein ultraviolet-Cradiation reflected from said walls is received by said at least onesensor.
 8. A method of disinfecting an area using ultraviolet radiationas described in claim 7, wherein said ultraviolet-C radiation is emittedfrom a location that is remote from said plurality of walls, and said atleast one sensor receives reflected radiation from said plurality ofwalls.
 9. A method of disinfecting an area using ultraviolet radiationas described in claim 8, wherein said at least one sensor is positionedat a location that is remote from said plurality of walls.
 10. A methodof disinfecting an area using ultraviolet radiation as described inclaim 7, wherein said room further comprises a ceiling, andultraviolet-C radiation is emitted from a location that is remote fromsaid plurality of walls, and said at least one sensor receives reflectedradiation from said plurality of walls and from said ceiling.
 11. Amethod of disinfecting an area using ultraviolet radiation as describedin claim 10, wherein said at least one sensor is positioned at alocation that is remote from said plurality of walls.
 12. A method ofdisinfecting an area using ultraviolet radiation as described in claim6, wherein said method comprises providing at least two sensors thatreceive only reflected ultraviolet-C radiation from said emission ofultraviolet-C radiation, and wherein a level of reflected ultraviolet-Cradiation received by each of said at least two sensors is measured forsaid each of said at least two sensors, and the emission ofultraviolet-C radiation is terminated after determining that a minimumcumulative level of reflected ultraviolet-C radiation has been receivedby said each of said at least two sensors.
 13. A method of disinfectingan area using ultraviolet radiation as described in claim 6, whereinsaid at least one ultraviolet-C radiation sensor is positioned toreceive reflected ultraviolet-C radiation from 360 degrees around saidat least one ultraviolet-C radiation sensor.
 14. A device fordisinfecting an area using ultraviolet radiation, comprising: (a) atleast one ultraviolet-C emitter which emits ultraviolet-C radiationwhich is subsequently reflected by a surface in the area; and (b) atleast one ultraviolet-C radiation sensor that is positioned relative tosaid at least one ultraviolet-C emitter to receive only reflectedultraviolet-C radiation.
 15. A device for disinfecting an area usingultraviolet radiation as described in claim 14, wherein said at leastone ultraviolet-C radiation sensor measures ultraviolet-C radiationreceived by said at least one ultraviolet-C radiation sensor, and saiddevice comprises means for terminating an emission of ultraviolet-Cradiation from at least one ultraviolet-C radiation emitter upondetermining that a cumulative level of reflected ultraviolet-C radiationhas been received by said at least one ultraviolet-C radiation sensor.16. A device for disinfecting an area using ultraviolet radiation asdescribed in claim 14, wherein said device comprises at least twoultraviolet-C radiation sensors that are positioned relative to said atleast one ultraviolet-C radiation emitter to receive only ultraviolet-Cradiation that is emitted by said at least one ultraviolet-C radiationemitter and is subsequently reflected, and said device comprises meansfor terminating an emission of ultraviolet-C radiation from said atleast one ultraviolet-C radiation emitter upon determining that acumulative level of reflected ultraviolet-C radiation has been receivedby each of said at least two ultraviolet-C radiation sensors.
 17. Adevice for disinfecting an area using ultraviolet radiation as describedin claim 14, wherein said at least one ultraviolet-C radiation emitteris positioned to direct ultraviolet-C radiation 360 degrees around saidat least one ultraviolet-C radiation emitter and above said at least oneultraviolet-C radiation emitter, and said at least one ultraviolet-Cradiation sensor is positioned to receive reflected ultraviolet-Cradiation from 360 degrees around said at least one ultraviolet-Cradiation emitter.
 18. A device for disinfecting an area usingultraviolet radiation as described in claim 14, wherein said at leastone ultraviolet-C radiation sensor measures ultraviolet-C radiationreceived by said at least one ultraviolet-C radiation sensor, and thedevice further comprises a computer, wherein said computer terminates anemission of ultraviolet-C radiation from said at least one ultraviolet-Cradiation emitter upon determining that a cumulative level of reflectedultraviolet-C radiation has been received by said at least oneultraviolet-C radiation sensor.
 19. A device for disinfecting an areausing ultraviolet radiation as described in claim 14, wherein the devicecomprises at least two sensors that are positioned to receive onlyultraviolet-C radiation that is emitted by said at least oneultraviolet-C radiation emitter and is subsequently reflected, and thedevice comprises a computer, wherein said computer terminates anemission of ultraviolet-C radiation from said at least one ultraviolet-Cradiation emitter upon determining that a cumulative level of reflectedultraviolet-C radiation has been received by each of said at least twoultraviolet-C radiation sensors.
 20. A device for disinfecting an areausing ultraviolet radiation as described in claim 14, wherein said atleast one ultraviolet-C radiation emitter and said at least oneultraviolet-C radiation sensor are positioned in a room, wherein saidroom comprises walls, and wherein said at least one ultraviolet-Cradiation sensor is positioned remotely from said walls.